The traditional distinction between amount and number is that amount is used with mass or uncountable nouns (the amount of paperwork; the amount of energy) and number with countable nouns (a number of songs; a number of days). Although objected to, the use of amount instead of number with countable nouns occurs in both speech and writing, especially when the noun can be considered as a unit or group (the amount of people present; the amount of weapons) or when it refers to money (the amount of dollars paid; the amount of pennies in the till).